The present invention relates to the making of stranded electrical cables.
Stranded cables are usually constructed with a reversing pitch; or at least, this is generally so desired. Stranding is provided by running individual stranding elements through the bores of a stationary guide disk. These stranding elements are then run through a reversibly revolving disk which is also provided with such guide bores. The central area between the two disks is occupied, e.g., by a smooth wall tube about which the elements are stranded. A stranding head is disposed downstream from the revolving disk.
Cables within the pertinent field of art are, for example, communication cables, or other multiconductor cables or bundles. Stranding elements are, correspondingly, leads and conductors but also conductor bundles such as pairs, quads or even larger bundles.
Stranding with a reversing twist (SZ-stranding) is superior to stranding with a uniform twist because one does not need revolving take-up spools.
Canadian Pat. No. 963 361 discloses a stranding machine which includes a stationary disk and a revolving disk, and the stranding elements are run through hoses between these disks. These hoses are made of a material having a very low coefficient of friction; they prevent bunching and tangling of the stranding elements. This approach is disadvantaged by the fact that initially a rather complicated procedure of threading long portions of the stranding elements into and through these hoses is required. Also, some friction is inevitable, leading to a fairly rapid wear-out of the hoses, requiring their frequent exchange. Also, some entanglements must also be expected, particularly if the two disks are rather far apart.
The German Pat. No. 26,15,275 describes a device for stranding elements which, by themselves, are SZ-stranded bundles. The device includes a stationary guide disk and a revolving disk, each one being circumscribed by an annulus which is also provided with apertures. An outer guide tube extends between these two disks, being held by the annular gaps between the respective disk and the circumscribing annulus. A second tube of smaller diameter extends between the two disks so that there remains a rather large gap between the two tubes. Stranding is carried out with two sets of stranding elements; one set or group runs through the apertures in the annuli, the other one through the apertures in the disks, extending all the while in that gap between the tubes while the first set of elements extends outside but along the larger tube. This device thus strands in two layers. Bundle cables of the type shown for communications in German Pat. No. 15,15,812 cannot be made in that manner. Moreover, the device of German Pat. No. 26,15,275 does not lend itself readily to the inclusion of a colored lay for identifying the individual lays.
German printed patent application No. 24 11 151 illustrates a device being closest to the summary description above. As per this publication, a core is made by stranding elements without a reversing twist, and additional stranding elements are then placed on top, but now with a reversing twist. The machine for the latter operation includes the two disk arrangements as mentioned. This structure permits stranding of but one lay onto such a core that is concurrently formed.